Stabilizer of drawing die and stabilizer unit of the same

ABSTRACT

An object of the invention is to standardize a stabilizer of a drawing die, to easily manufacture and to achieve a cost reduction. The invention provides a stabilizer of a drawing die that includes a punch, a blank holder outside fitted to the punch and supported by a cushion pin and provided so as to freely move upward and downward, and a die arranged so as to face to the punch and moves upward and downward, and with which a thin plate mounted on the blank holder moved upward by the cushion pin and pinched between the blank holder and the die by moving the die downward is drawn by the punch, wherein a plurality of boxes are arranged around the blank holder between the cushion pin and the blank holder so as to be freely moved upward and downward by the cushion pin, a buffer gas spring is interposed between the boxes and the blank holder so as to form a run-up gap of the blank holder between the boxes and the blank holder, a run-up lever pressing the blank holder so as to make the blank holder run up before the die comes into collision with the thin plate on the blank holder is rotatably provided in the boxes, and a driver driving the run-up lever is arranged at a position facing to the run-up lever of the die, whereby the die comes into collision with the thin plate on the blank holder after the blank holder runs up.

BACKGROUND OF THE INVENTION

The present invention relates to a stabilizer of a drawing die and a stabilizer unit of the same.

A known drawing die is shown in FIG. 5.

The drawing die is constituted by a punch 101 positioned at the center, a blank holder 103 outside fitted to the punch 101, supported by a cushion pin 102 and provided so as to freely move upward and downward, and a die 104 arranged so as to face to the punch 101 and moving upward and downward. Reference numeral 105 denotes an air vent.

A lower die 109 constituted by the punch 101 and the blank holder 103 is fixed to a bolster 106 of a press machine, an upper die 110 constituted by the die 104 is fixed to a ram 107 of the press machine, and the upper die 110 is moved upward and downward by driving the press machine. Further, the blank holder 103 is supported by the cushion pin 102, the cushion pin 102 is moved upward and downward by a cushion apparatus of the press machine, and accordingly, the blank holder 103 moves upward and downward.

A description will be given of a drawing process. First, the blank holder 103 is moved upward to a position shown by a double-dashed line by the cushion pin 102.

Next, as shown by a double-dashed line, a thin plate 108 is mounted on the blank holder 103 and the punch 101.

Thereafter, when moving the upper die 110 downward, the die 104 comes into collision into the thin plate 108 on the blank holder 103 in an entire outer periphery of the punch 101 so as to pinch the thin plate 108 by the blank holder 103 and the die 104. Subsequently, when the upper die 110 moves downward, the thin plate 108 pinched by the blank holder 103 and the die 104 is drawn by the punch 101. Further, when the upper die 110 reaches an illustrated bottom dead center, the thin plate 108 is formed in a work W.

When the upper die 110 moves upward, the blank holder 103 is moved upward to a state shown by a double-dashed line on the basis of an ascending force of the cushion pin 102, and the work W is taken off from the punch 101. The upper die 110 is structured such that the air vent 105 is provided in the die 104 so as to prevent a negative pressure from being generated between the work W and the die 104 at a time when the work W comes down by an empty weight. Alternatively, the work W is moved to a lower side by an extrusion pin (not shown) energized by a spring, the work W is taken off from the die 104, and the work W picked up from the press machine is transferred to a press machine in the next step.

In the drawing process mentioned above, when the die 104 comes into collision into the thin plate 108 mounted on the blank holder 103, the thin plate 108 extending around an entire surface of an entire outer periphery of the punch 101 (that is, the thin plate 108 on the blank holder 103) and the die 104 are simultaneously brought into contact and are worked in an impact manner at a breath. Accordingly, it is necessary to use a high-quality thin plate which can sustain the impact. Further, a service life of the press die and the press machine is shortened due to the impact process.

Even when low quality process material is used, it is required that the processed product has the same quality as when high quality process material is used, and that the product cost is reduced.

In the drawing die, a great impact is generated at a time when the die comes into collision with the thin plate on the blank holder, however, in order to make the service life of the drawing die and the press machine long, it is desired to make the impact as small as possible.

If the stabilizer of the drawing die is standardized, it is easy to manufacture, and a cost reduction can be achieved.

Further, at a time of executing the drawing process, a loud noise is generated at a time when the upper die and the lower die come into collision.

Further, when the blank holder finishes the upward movement after the drawing process is executed, a vibration is generated in the work on the blank holder.

In view of the above noted problems, the present invention is made in order to make the impact generated in the drawing die as small as possible, make it possible to make the processed product have the same quality as when high quality process material is used even when low quality process material is used so as to achieve the cost reduction of the product, and to make the service life of the drawing die and the press machine long, standardize the stabilizer of the drawing die so as to easily manufacture so as to achieve the cost reduction. To this end, the present invention provides a stabilizer of a drawing die that includes a punch, a blank holder outside fitted to the punch and supported by a cushion pin and provided so as to freely move upward and downward, and a die arranged so as to face to the punch and moves upward and downward, and with which a thin plate mounted on the blank holder moved upward by the cushion pin and pinched between the blank holder and the die by moving the die downward is drawn by the punch, wherein a plurality of boxes are arranged around the blank holder between the cushion pin and the blank holder so as to be freely moved upward and downward by the cushion pin, a buffer gas spring is interposed between the boxes and the blank holder so as to form a run-up gap of the blank holder between the boxes and the blank holder, a run-up lever pressing the blank holder so as to make the blank holder run up before the die comes into collision with the thin plate on the blank holder is rotatably provided in the boxes, and a driver driving the run-up lever is arranged at a position facing to the run-up lever of the die, whereby the die comes into collision with the thin plate on the blank holder after the blank holder runs up.

In particular, the stabilizer of a drawing die according to the present invention, is such that a cam surface of an angle of incline changing a speed is provided.

Further, in order to easily improve the existing drawing die, a stabilizer unit of a drawing die according to the present invention is structured such as to be attached to the boxes and the die and come into collision with the boxes after making the blank holder run up.

In addition, in order to easily improve the existing drawing die, the stabilizer unit of a drawing die according to the present invention includes a run-up lever and a driver driving the run-up lever.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross sectional view of a main portion showing a state in which an operation of the run-up lever in accordance with the present invention is started;

FIG. 2 is a side elevational view of a stabilizer of a drawing die in FIG. 1;

FIG. 3 is a vertical cross sectional view of a main portion showing a state in which a blank holder in accordance with the present invention runs up and is brought into contact with a block and a die is joined to a thin plate on the blank holder;

FIG. 4 is a vertical cross sectional view of a main portion showing a state of a bottom dead center in which an upper die moves further downward from the state in FIG. 3 of the present invention, and the drawing is finished; and

FIG. 5 is a vertical cross sectional view of a conventional drawing die.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description of the present invention will be given in detail below on the basis of a particular embodiment shown in accompanying drawings.

In FIG. 1, a lower die 1 is constituted by a punch 2, a blank holder 3 outside fitted to the punch 2 and provided so as to be freely moved upward and downward by a cushion pin 4, and a plurality of boxes 5 outside fitted to the punch 2 in the same manner and supported to the cushion pin 4 around the blank holder 3.

Conventionally, a sub blank holder constituted by an annular ring-like integrally formed member outside fitted to the punch 2 has been used, however, a drawing die becomes large by using the sub blank holder, and too much cost is required. Therefore, in accordance with the present invention, the structure is made such that the plurality of standardized boxes 5 are arranged only at necessary positions below the blank holder 3 around the punch 2. A number of the boxes needed is determined according to a size of the drawing die, and generally, four to six boxes are arranged.

An upper die 6 is constituted by a die 7 arranged so as to face to the punch 2.

A buffer gas spring 11 is interposed between the box 5 and the blank holder 3 of the lower die 1 so as to form a gap making the blank holder 3 float over the box 5, and the gap is set to a run-up gap H₁. In this case, the buffer gas spring 11 is fastened into the box 5 by a bolt 8.

The buffer gas spring 11 employs a gas-pressure/hydraulic cylinder, and a stroke and an output of a piston 12 of the buffer gas spring 11 are determined in correspondence to the drawing die. The buffer gas spring 11 is also standardized. Although an output of one cushion pin 4 is normally about 100 ton, one buffer gas spring 11 has an output of 6 ton and a stroke of about 15 mm.

A run-up lever 13 which is approximately in a triangular shape and presses the blank holder 3 so as to make the blank holder 3 run up is rotatably provided in a bracket 14. The bracket 14 is fixed to the box 5 by a bolt 15, and a positioning groove 16 is provided for making an attaching position of the bracket 14 accurate.

There is provided a stabilizer unit of a drawing die which is attached to the box 5 and the die 7 and making the blank holder 3 come into collision with the box 5 after making the blank holder 3 run up. An example thereof will be illustrated.

The run-up lever 13 is provided so as to be rotatable around a rotary shaft 17 provided in the bracket 14, and presses a flange 18 of the blank holder 3. A pressing surface 19 of the run-up lever 13 is provided with a hardened pressing member 20, and a hardened pressure receiving member 9 is provided at a part of the flange 18 where the pressing member 20 is brought into contact.

A roller 21 is rotatably provided in an upper portion of the run-up lever 13, and a roller 22 is provided at a position facing the roller 21 in the bracket 14 so as to be rotatable around a rotary shaft 47.

A driver 31 is provided at a position of the facing die 7 between the roller 21 and the roller 22. The driver 31 is attached to the die 7 via a support table 32. The support table 32 is fastened to the die 7 by a bolt 33, and the driver 31 is fastened to the support table 32 by a bolt 34. The driver 31 and the support table 32 may be manufactured as an integral member.

The driver 31 has a cam surface 35 including a low speed angle of incline α and a middle speed angle of incline β that are provide continuously. The low speed angle of incline α is close to a right angle to a part of the upper die 6 that is brought into contact with the roller 21 at an initial time when the upper die 6 moves downward. A connection portion between the low speed angle of incline α and the middle speed angle of incline β are smoothly connected by a circular arc. It is possible to control downward moving speeds of the run-up lever 13 and the blank holder 3 by changing the low speed angle of incline α and the middle speed angle of incline β of the driver 31.

FIG. 2 shows a side view of the stabilizer of the drawing die in FIG. 1.

An appropriate number of blocks 5 are arranged in a standardized manner in the lower portion of the blank holder 3 around the punch 2, and are made movable upward and downward by the cushion pin 4.

The bracket 14 is firmly fixed to the block 5 by the bolt 15, and side plates 41 are arranged at both outer sides of the bracket 14. Further, the side plates 41 are fastened to the flange 18 of the blank holder 3 by bolts 42 and 43.

The rotary shaft 17 is extended through a base end of the run-up lever 13, a base end portion of the run-up lever 13 is received within the bracket 14, and each end portion of the rotary shaft 17 is inserted through a long hole 44 of each side plate 41 and is fastened by a bolt 46 via a washer 45.

The roller 22 that is provided rotatably around the rotary shaft 47 is received in the upper portion of the bracket 14. Both ends of the rotary shaft 47 are supported by the bracket 14, both end surfaces are stopped by stop plates 48, and each stop plate 48 is fastened to the bracket 14 by a bolt 49.

The buffer gas spring 11 is fastened to the block 5 by the bolt 8, and a piston 50 of the buffer gas spring 11 is brought into contact with a lower surface of the flange 18 of the blank holder 3. The flange 18 of the blank holder 3 is lifted up at a run-up gap H₁, 15 mm, for example, from the upper surface of the block 5 on the basis of the output of the buffer gas spring 11.

Next, a description will be given of an operation.

The thin plate 51 is mounted on the punch 2 and the blank holder 3.

FIG. 1 shows a state in which the upper die 6 moves downward, and the run-up lever 13 starts being brought into contact with the flange 18 of the blank holder 3 by the driver 31. An operation starting gap H₂ of the blank holder 3 and the die 7 in FIG. 1 is set larger than the run-up gap H₁ in order to make the blank holder 3 run up first, and then come into collision with the block 5. The run-up gap H₁, the operation starting gap H₂, and a relation between the run-up gap H₁ and the operating starting gap H₂ (a degree at which the operation starting gap H₂ is larger than the run-up gap H₁) are set to values that is sufficient to avoid an impact work.

After the blank holder 3 is made run up by the run-up lever 13, and presses the piston 50 of the buffer gas spring 11 and the lower surface of the flange 18 of the blank holder 3 is brought into contact with the upper surface of the block 5, the die 7 is brought into contact with the thin plate 51 on the blank holder 3. The state at this point is shown in FIG. 3. In the case of H₁=15 mm, for example, the contact portion of the run-up lever 13 with the flange 18 of the blank holder 3 moves downward at a distance of 15 mm, an a relation that H₁=0 mm is established. The die 7 is brought into contact with the thin plate 41 on the blank holder 3 that is running up, not in resting state. Since the die 7 is brought into contact with the thin plate 51 that is running up, and not coming into collision with the thin plate 51 that is in static condition, an impact is hardly generated.

Thereafter, the upper die 6 continuously moves downward, the drawing process is finished in a state of a bottom dead center shown in FIG. 4, and the work W is formed. In the case of the present embodiment, the cushion pin 4 moves downward at a distance of 65 mm.

When the upper die 6 moves upward, the work W is taken out of the punch 2 by the blank holder 3, and an air vent 52 is provided in the die 7 so as to prevent a negative pressure from being generated between the work W and the die 7 at a time when the work W comes down due to an empty weight. Alternatively, the work W may be discharged out of the die 7 by an extrusion pin (not shown) energized by a spring.

If the block 5, the run-up lever 13, the bracket 14, the driver 31 and the like (including the roller 21, the roller 22, the rotary shaft 17, the buffer gas spring 11, and the support table 32) are set as standardized parts and various parts are provided in correspondence to the size, it is possible to easily change the existing drawing die to the die having the buffer structure.

In accordance with the present invention, since the components of the stabilizer of the drawing die such as the block are provided in a standardized manner, the buffer structure can be easily provided for any drawing die. Even when low quality process material is used, it is possible to make the processed product have the same quality as when high quality process material is used, and it is possible to achieve a cost reduction of the product.

Further, in accordance with the present invention, since the die comes into collision with the thin plate on the running up blank holder, a noise can be reduced.

Further, in accordance with the present invention, since the blank holder executing the drawing process by the stabilizer unit moves upward step by step, it is possible to reduce a vibration of the work on the blank holder.

In accordance with the present invention, there is provided the stabilizer of a drawing die that includes a punch, a blank holder outside fitted to the punch and supported by a cushion pin and provided so as to freely move upward and downward, and a die arranged so as to face to the punch and moves upward and downward, and with which a thin plate mounted on the blank holder moved upward by the cushion pin and pinched between the blank holder and the die by moving the die downward is drawn by the punch, wherein a plurality of boxes are arranged around the blank holder between the cushion pin and the blank holder so as to be freely moved upward and downward by the cushion pin, the buffer gas spring is interposed between the boxes and the blank holder so as to form the run-up gap of the blank holder between the boxes and the blank holder, the run-up lever pressing the blank holder so as to make the blank holder run up before the die comes into collision with the thin plate on the blank holder is rotatably provided in the boxes, and the driver driving the run-up lever is arranged at the position facing to the run-up lever of the die, whereby the die comes into collision with the thin plate on the blank holder after the blank holder runs up. Accordingly, it is possible to make the impact generated in the drawing die as small as possible, to make the processed product has the same quality as when high quality process material is used, even when low quality process material is used, so as to achieve the cost reduction of the product, to make the service life of the drawing die and the press machine long, to easily manufacture by standardizing the stabilizer of the drawing die, and to achieve the cost reduction, Further, in accordance with the present invention, there is provided the stabilizer of the drawing die, wherein the cam surface of the angle of incline changing the speed is provided. Accordingly, it is possible to control the run-up speed of the blank holder.

Further, in accordance with the present invention, there is provided the stabilizer unit of the drawing die structured such as to be attached to the boxes and the die and come into collision with the boxes after making the blank holder run up. Accordingly, it is possible to easily improve the existing drawing die. If the stabilizer unit is standardized, the drawing die can be easily manufactured, and it is possible to achieve the cost reduction.

Further, in addition, in accordance with the present invention, there is provided the stabilizer unit of the drawing die, wherein the run-up lever and the driver driving the run-up lever are provided. Accordingly, it is possible to easily improve the existing drawing die. Further, if the stabilizer unit is standardized, the drawing die can be easily manufacture, and it is possible to achieve the cost reduction. In accordance with the present invention, since the die comes into collision with the thin plate on the running up blank holder, it is possible to reduce the noise.

Further, in accordance with the present invention, since the blank holder executing the drawing process moves upward step by step by the stabilizer unit, it is possible to reduce the vibration of the work on the blank holder.

The present invention is described about the drawing die, however, may be applied to a forming die.

EMBODIMENT

The size of the block is 150 mm×275 mm×120 mm height. 

1. A stabilizer of a drawing die that includes a punch, a blank holder outside fitted to the punch and supported by a cushion pin and provided so as to freely move upward and downward, and a die arranged so as to face to the punch and moves upward and downward, and with which a thin plate mounted on the blank holder moved upward by the cushion pin and pinched between the blank holder and the die by moving the die downward is drawn by the punch, wherein a plurality of boxes are arranged around the blank holder between the cushion pin and the blank holder so as to be freely moved upward and downward by the cushion pin, a buffer gas spring is interposed between the boxes and the blank holder so as to form a run-up gap of the blank holder between the boxes and the blank holder, a run-up lever pressing the blank holder so as to make the blank holder run up before the die comes into collision with the thin plate on the blank holder is rotatably provided in the boxes, and a driver driving the run-up lever is arranged at a position facing to the run-up lever of the die, whereby the die comes into collision with the thin plate on the blank holder after the blank holder runs up.
 2. A stabilizer of a drawing die as claimed in claim 1, wherein the driver is provided with a cam surface of an angle of incline changing a speed.
 3. A stabilizer unit of a drawing die structured such as to be attached to the boxes and the die as claimed in claim 1 and come into collision with the boxes after making the blank holder run up.
 4. A stabilizer unit of a drawing die as claimed in claim 3, comprising: a run-up lever; and a driver that drives the run-up lever. 